The leatherback is the largest sea turtle in the world. An average adult can measure up to 5 feet (1.5 meters) long and weigh between 800 and 1,000 pounds (363 and 454 kilograms). Other marine turtles have hard, bony–plated shells, or carapaces (pronounced KAR–a–paces).

The dark brown to black carapace of the leatherback sea turtle is made of seven raised ridges that are soft and rubbery. Its front flippers are exceptionally long and powerful. When extended, they may span over 8 feet (2.4 meters). The turtle’s head and neck are dark brown or black with white or yellowish blotches.